Neutral emission

The effect of water (0.003 mole fraction) and methanol (0.02 mole fraction) cosolvents on the emission of 5CN2N is shown in Figure 4. For this probe there is complete loss of fine structure, a significant red shift in the neutral emission with methanol cosolvent, but again, no detectable anion emission. 

We suggest the following possible reasons for the absence of anion emission in these experiments First, it is possible for water and methanol to form adducts with CO2 which might inhibit their ability to solvate the proton. This possibility was checked using water as a cosolvent in supercritical ethylene, which will not interact with water data do not indicate formation of an anion therefore solvent/cosolvent adducts are not a plausible explanation. Second, perhaps the anion is being formed but is quenched very efficiently. The anion species would be more susceptible to quenching than the neutral molecule. This possibility could be investigated in principle with fluorescence lifetime studies, but this has not been done. It is entirely possible that the anion emission is so weak as to be hidden underneath the tail of the neutral emission. 

The identifications of atomic and molecular species is undertaken with a variety of mass spectroscopies. Time-of-flight (TOF) mass spectroscopy is of value for very short lived or highly peaked emissions. More sustained emissions are more readily studied with a quadrupole mass spectrometer (QMS), which can be tuned to a single mass peak. The time evolution (on a microsecond time scale) of a particular mass emission can be determined from the observed signals. Under the appropriate conditions, both these tools can be applied to studies of neutral emission (with ionizer) and positive or negative ion emission (without ionizer). 

Significant neutral emission is also observed during and after fracture. When analyzing the time dependence of the observed NE, one must take into account both the time dependence of the emission itself and the time-of-flight of the neutral species (associated with Boltzmann velocity distributions) from the source to the mass spectrometer. We expect NE intensities to be much higher than the PIE intensities of the same molecular species due to the high probability of reneutralization as ions leave the surface. NE will be discussed more fully in the following section. 

Neutral emission of species other than atomic Mg from MgO is a strong function of impurity content or microstructure (4). Samples with a cloudy appearance due to the presence of brucite (Mg(OH)2) precipitates, displayed especially high NE intensities of O2, CO, H2O, and CH4. The cloudy MgO is nominally as pure as the clear with respect to metallic impurities. Single crystals of MgO are often grown in an arc furnace, with water and carbon as minor impurities. Small amounts of brucite can precipitate in portions of the crystal mass. The precipitate/MgO interface can serve as a sink for many species which are then emitted as these interfaces are exposed in fracture. The cloudy MgO is more typical of geologic materials than clear MgO, implying that NE from geologic materials can be quite intense and rich. 

Atomic and molecular neutral emissions could also be a source of some chemical species released on astronomic and geologic scales. The release of metal... 

Many attempts have been made to obtain spectra of meteor trails. Probably the best spectra ever obtained were by Millman and his colleagues at the Dominion Observatory. Figures 4 and 5 are a comparison of spectra stemming from a slow (probably Giacobinid) and a fast (Perseid) meteor, respectively. The spectrum of the low velocity meteor exhibits neutral emission lines of Mg, Fe, and Ca, the most abundant metals in most meteoroids. The strong Na D lines as well as a hint at excited N2 are also visible. By contrast, the spectrum of the high velocity meteor shows very... 

In a water-alcohol mixture, the deprotonation rate of protonated aminopyrene increases with alcohol concentration up to about 65-70%, whereas it decreases at higher alcohol concentrations [36]. However, for 1-naphthol, the deprotonation rate decreases monotonically as the alcohol content increases [38]. At high alcohol content the rise time of the anion of 1-naphthol is faster than the decay of the neutral form. This indicates that in alcohol-water mixtures, the anion (460 nm) and the neutral emission (360 nm) originate from different 1-naphthol molecules. 

Preliminary time-resolved fluorescence measurements give a somewhat better indication of what the cage lifetime might be. ° Both the rise in the fluorescence of the anion and the decay of neutral emission of 8-hydroxy-1,3,6-pyrene were measured. Careful examination of both the rise of the anion and the decay of the neutral indicate the presence of biphasic behavior. The biphasic kinetics can more readily be seen in DjO. It is quite possible that the faster rate constant is due to protons that immediately escape the cage, while the slower decay is due to the destruction of the cage. 

The neutral emission (NE) species are sensitive to the chemical composition of the fracture material. For... 

Negative ion yield is proportional to the electron affinity of the element. Sputter yield depends on the difference between electron affinity of the desired atom and the effective work function. Work function varies upon the environment of the surface of the sample. Physical conditions of the sample affect the properties of atoms on the surface. The probability of negative ion formation is enhanced by the presence of Cs layer at the surface of the sample and electron cloud near the sample surface. Samples are mixed with metallic powder (e.g., Ag or Nb) to improve the thermal and electrical conductivity. Ion-atom collision kinematics reduces the sputter yield for heavy elements. Production of negative ions is at the maximum for normal incidence of the sputtering beam, but the total sputter rate, which means positive, negative, and neutral emission, increases when the angle of incidence is away from the normal. Atomic ion current is very low or zero for some elements. In that case, selection of one molecular ion out of many possible molecular ions (like oxides, hydrides, or carbides) becomes important (Tuniz et al. 1998). 

Orecchini, F., Bocci, E., and di Carlo, A. (2008) Process simulation of a neutral emission plant using chestnut s coppice gasification and molten carbonate fuel... 

Neutral emission accompanying fracture has two origins (a) basically degassing from a freshly exposed surface of gases that are trapped in the material (within voids, grain boundaries, inclusions, etc.) and (b) species resulting from bond scissions (sometimes referred to as... 

J. T. Dickinson and L. C. Jensen, Neutral emission from the fracture of epoxy, J. Appl. Phys. (to be submitted). 

Energy filters, covered in Section 4.23.2, also act to ensure that no line of sight exists between the sample and the detector. This is required to remove the secondary neutral emission also produced during the sputtering process. Note As secondary neutrals in the secondary ion beam cannot be mass filtered (these are unaffected by electrostatic and magnetic fields), they will introduce a background signal if not removed. 

The price of incineration will rise continuously due to the necessity of automatically controlling combustion, the development of burning in suspension, and the control of the emission of toxic gases and their neutralization. Emission limits in French incinerators are given in Table 13 [433]. 

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